Watts to Kilowatt-Hours (kWh) Electrical Conversion Calculator

Convert watts to kilowatt-hours by entering power in watts and time in hours.

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How to Convert Watts to Kilowatt-Hours

A kilowatt-hour, expressed as kWh, is a measure of energy that is equivalent to 1,000 watts of power for a 1 hour time period. Thus, to convert watts to kilowatt-hours, multiply the power in watts by the number of hours, then divide by 1,000.

Use the following formula to calculate kWh:

kWh = (watts × hrs) ÷ 1,000

For example: let’s find the kWh of 1,500 watts for 2.5 hours.

kWh = (1,500 × 2.5) ÷ 1,000
kWh = 3,750 ÷ 1,000
kWh = 3.75

Electricity usage is often measured in watt-hours or kilowatt-hours, so if you can convert watts to kWh then you can predict how much an electric appliance might cost, or how much energy is required to power it.

For example: let’s predict how much it costs to power a light bulb every hour. A 100 watt light bulb uses 100 watts of power. To convert the power in watts to kilowatt-hours, multiply 100 watts by 1 hour, then divide by 1,000 to find the energy usage in kWh.

Energy = (100 × 1) ÷ 1,000
Energy = 100 ÷ 1,000
Energy = 0.1 kWh

If electricity costs $0.12 per kWh, then a 100 watt light bulb will cost 1.2 cents per hour that it’s on.

Common Watts to Kilowatt-Hour Conversions

Common watts to kilowatt-hour conversions for a 1-hour time period, along with the estimated cost of electricity assuming a price of $0.12 per kWh.
Power in Watts Energy in Kilowatt-hours Electricity Cost
100 W 0.1 kWh $0.012 per hr
200 W 0.2 kWh $0.024 per hr
300 W 0.3 kWh $0.036 per hr
400 W 0.4 kWh $0.048 per hr
500 W 0.5 kWh $0.060 per hr
600 W 0.6 kWh $0.072 per hr
700 W 0.7 kWh $0.084 per hr
800 W 0.8 kWh $0.096 per hr
900 W 0.9 kWh $0.108 per hr
1000 W 1 kWh $0.112 per hr

Need to convert to watts? Use our kWh to watts conversion calculator.